Vehicle systems and methods for detecting pedestrian impacts

ABSTRACT

Systems and methods for pedestrian impact detection are provided. Piezoelectric sensor elements detect an object impacting a vehicle. The detected signal is attenuated and filtered. The attenuated and filtered signal is analyzed in the frequency domain to determine whether the object which impacted the vehicle is a pedestrian. If the object which impacted the vehicle is a pedestrian, then a pedestrian protection system is deployed.

BACKGROUND OF THE INVENTION

Motor vehicles are typically equipped with a variety of sensors, some ofwhich are used to activate systems which protect vehicle occupants.These systems are known as passive restraint systems, and include frontand side airbags, seatbelt pretensioners, and the like.

Recently investigation has begun on systems which protect pedestriansinvolved in a vehicle collision. For example, US Patent ApplicationPublication No. 2004/0066286 A1 discloses a system for sensing whetheran object, which struck a vehicle, is a pedestrian. If it is determinedthat a vehicle has struck a pedestrian, the system activates a collisionprotection apparatus such as an external inflatable member to protectthe pedestrian from impacting the vehicle hood, and shifting the hoodinto a raised position that permits it to absorb forces applied by thepedestrian impact. Whether to deploy the collision protection apparatusdepends upon the location and length of the impact to the vehicle.

Another technique for detecting object impact is using a piezoelectriccable sensor. Using this technique, the magnitude of a signal from thepiezoelectric cable sensor is compared to a threshold value. If themagnitude is greater than a threshold value, it is determined that aparticular type of object has impacted on the sensor. However, due tothe overlap in signals between different types of objects, thepiezoelectric cable sensor technique is not able to accuratelydistinguish between different types of objects.

There are two critical components to the aforementioned pedestrianimpact protection systems—speed and accuracy of the impact detection.With regard to the speed component, if a decision to deploy a pedestrianimpact protection system is not timely, it may not deploy fast enough toprovide the desired protection for the pedestrian. Furthermore, due tothe costs involved with replacing airbags or resetting other types ofpedestrian impact protection systems, it is desirable that these systemsare only deployed when there is an actual pedestrian impact.Accordingly, it would be desirable to provide systems and methods forquickly and accurately detecting pedestrian impacts.

SUMMARY OF THE INVENTION

Systems and methods for pedestrian impact detection are provided. Inaccordance with exemplary embodiments of the present invention,piezoelectric sensor elements detect an object impacting a vehicle. Thedetected signal is attenuated and filtered. The attenuated and filteredsignal is analyzed in the frequency domain to determine whether theobject which impacted the vehicle is a pedestrian. If the object whichimpacted the vehicle is a pedestrian, then a pedestrian protectionsystem is deployed.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. 1 illustrates an exemplary piezoelectric sensor in accordance withthe present invention;

FIG. 2 illustrates a simplified circuit diagram of an exemplarypiezoelectric object impact sensor system in accordance with the presentinvention;

FIG. 3 is a logical representation of the exemplary piezoelectric objectimpact sensor system in accordance with the present invention;

FIG. 4 illustrates an exemplary object type identification circuit inaccordance with the present invention;

FIG. 5 is a logical representation of the object impact detection systemin accordance with exemplary embodiments of the present invention; and

FIG. 6 is an exemplary method for identifying a type of object impact inaccordance with exemplary embodiments of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates an exemplary piezoelectric sensor 100 in accordancewith the present invention. The sensor 100 includes a plurality ofpiezoelectric sensor elements 110 embedded in a dielectric layer 130.Each of the piezoelectric sensor elements 110 are coupled to a connector140 via a corresponding wire 120. Each of the wires is embedded in thedielectric layer 130. The number of sensor elements 110 can varydepending upon the particular vehicle. Additionally, although the sensorelements are illustrated in a one-dimensional array, THE presentinvention also includes sensor elements in a two- or three-dimensionalarray.

The piezoelectric sensor 100 is flexible enough to be integrated into avehicle bumper (or other appropriate vehicle component) and it iselectrically shielded to substantially eliminate effects ofelectro-magnetic (EM), radio frequency (RF), and other types ofelectro-magnetic interferences. As used herein, the phrase substantiallyeliminate is intended to mean minimize interferences which affectidentification of object types, while interferences which do not affectthe identification of object types may still be present.

FIG. 2 illustrates a simplified circuit diagram of an exemplarypiezoelectric object impact sensor system in accordance with the presentinvention. The circuit includes a piezoelectric sensor 210, a capacitor220, and a data acquisition circuit 230. The piezoelectric sensor 210provides an object detection signal U_(s), which is higher than limitsof sensor electronics. Therefore, the signal U_(s) is attenuated inorder to be adapted to the limits of sensor electronics. The attenuationis achieved by placing capacitor 220 in series with the piezoelectricsensor 210 and the data acquisition circuit 230, which is an RC element.Using this impedance circuitry, the distortion of the output signalU_(Sout) is minimized. The output signal U_(Sout) is used foridentifying the type of object impact. Although FIG. 2 illustratescapacitor 220 attenuating the impact detection signal, other types ofattenuators may be employed.

FIG. 3 is a logical representation of the exemplary piezoelectric impactsensor system in accordance with the present invention. As illustratedin FIG. 3, the exemplary impact sensor includes a plurality ofpiezoelectric sensor elements 310 a-310 x. Each of the piezoelectricsensor elements 310 a-310 x is coupled to a respective attenuationcircuit 320 a-320 x. Each of the attenuation circuits 320 a-320 xprovides an attenuated impact sensor signal to a respective analogfilter 330 a-330 x. The analog filters 330 a-330 x provide a filteredand attenuated impact sensor signal to the object type identificationcircuitry (not shown). The analog filters 330 a-330 x are designed suchthat they pass those frequencies which are useful for determiningwhether the impacted object is a pedestrian. In accordance withexemplary embodiments of the present invention, the passband is set toallow signals in the 100 Hz to 20 kHz to pass through the filter.

It should be recognized that the analog filters can be replaced bydigital filtering by converting the attenuated signal from an analogwaveform into a digital representation of the analog waveform. Thedigital representation can be filtered by a microprocessor operatingunder software control, an application specific integrated circuit(ASIC), field programmable gate array (FPGA), or the like.

FIG. 4 illustrates an exemplary object type identification circuit 400in accordance with the present invention. The object type identificationcircuit identifies whether an object, which impacted the vehicle, iseither a pedestrian or non-pedestrian object. However, the circuit canalso be extended to provide more precise identification ofnon-pedestrian objects.

The circuit 400 receives the filtered signal from the analog filters andconverts the analog signal into the digital domain using analog todigital (A/D) converter 410. The digital signal is provided to amicroprocessor 420 for analyzing the signal in the frequency domain. Inaccordance with exemplary embodiments of the present invention, themicroprocessor 410 performs under software control to perform the A/Dconversion to acquire the data, obtain vehicle information such as thevehicle speed, process the sensor signals, and provide an output signalto an object protection system (not illustrated) for deployment of theobject protection system. Microprocessor 420 can be a conventionalmicroprocessor operating under software control, ASIC, FPGA, or thelike.

FIG. 5 is a logical representation of the object impact detection systemin accordance with exemplary embodiments of the present invention. Thesystem includes the sensor strip component 510, sensor electronics 520and the object protection system 530. The sensor strip component 510includes the attenuation and filtering circuitry. The output of thesensor electronics 520 is provided directly, or through a communicationbus, to the object protection system 530. The object protection system530 can include a pedestrian airbag which deploys between the vehicleexterior and the pedestrian, a mechanism for shifting the hood to anelevated position, and/or any other system which protects a pedestrianduring a vehicle impact. Moreover, the sensor electronics output can beprovided to other vehicle safety systems such as airbag electronics orpassive restraint electronics.

FIG. 6 is an exemplary method for identifying a type of object impact inaccordance with exemplary embodiments of the present invention. When thepiezoelectric sensors are impacted, the system receives an impactdetection signal (step 610). The impact detection signal is attenuated(step 620) and filtered (step 630). The attenuated and filtered impactdetection signal is then processed to determine whether the impactsignal corresponds to a pedestrian impact (step 650). If the impactsignal does not correspond to a pedestrian impact (“No” path out of step650), then conventional processing is performed (step 660). Theconventional processing can include performing no further processing,providing the attenuated and filtered signal to other passive restraintsystems, providing the original impact detection signal to other passiverestraint systems, and/or the like. If, however, a pedestrian impact isdetected (“Yes” path out of decision step 650), then the pedestrianimpact protection system is activated (step 670).

A variation of the method of FIG. 6 can be to also account for the speedof the vehicle in determining whether to deploy the pedestrian impactprotection system. In accordance with this variation, after a pedestrianimpact has been detected (step 650), it is determined whether thevehicle is traveling within a predetermined speed value range. Thisspeed value can be provided to the object type identification circuitfrom a speed sensor. Speed sensors are known in the art. If the vehicleis traveling at a speed which is outside of the predetermined speedvalue range, then conventional processing is performed (step 660). If,however, the vehicle speed is within the predetermined speed valuerange, then the pedestrian impact protection system is activated (step670).

The piezoelectric object type identification system of the presentinvention provides a number of advantages over conventional systems. Forexample, the system provides a quick determination of whether the objectimpact is that of a pedestrian impact. Specifically, the system candetect pedestrian impacts within approximately 8 ms. Non-pedestrianimpacts such as car-to-car, rigid barrier, stone impact, styrofoam,plant, traffic sign, pylon, tennis ball, football are filtered out bythe analog filters. Accordingly, the detection time for suchnon-pedestrian impacts is much shorter than 8 ms because there will beno frequencies within the range of frequencies for pedestrian impacts tobe processed.

Moreover, the accuracy provided by the present invention in detection ofpedestrian impacts protects against improper activation of thepedestrian impact protection system, which can lead to costly repairsfor the vehicle owner and may obscure the driver's view. The presentinvention also provides cost savings in the sensor design by relyingupon piezoelectric sensor elements, which are cheaper than other typesof sensors such as piezoelectric cable sensors. Additionally, the sensoris easily integrated into a vehicle component, such as a bumper, whiletaking up minimal space.

While the invention has been described in connection with variousembodiments, it will be understood that the invention is capable offurther modifications. This application is intended to cover anyvariations, uses or adaptations of the invention following, in general,the principles of the invention, and including such departures from thepresent disclosure as known, within the known and customary practicewithin the art to which the invention pertains.

1. A system, comprising: a piezoelectric sensor; a filter coupled to thepiezoelectric sensor, wherein the filter produces a filtered signal byremoving predetermined frequency signals from a signal received from thepiezoelectric sensor; and an object type identification circuit coupledto the filter, wherein the object type identification circuit identifieswhether a particular type of object has impacted on the piezoelectricsensor based on an analysis of the filtered signal.
 2. The system ofclaim 1, further comprising: an object protection system, wherein if theobject type identification circuit determines that the particular typeof object has impacted on the piezoelectric sensor, then the objectprotection system is deployed.
 3. The system of claim 2, furthercomprising: a speed sensor, wherein the object protection system isdeployed when the particular type of object has impacted on thepiezoelectric sensor and the speed sensor outputs a speed value within apredetermined speed value range.
 4. The system of claim 1, wherein theparticular type of object is a pedestrian.
 5. The system of claim 1,wherein the piezoelectric sensor comprises a plurality of piezoelectricsensor elements, and the filter comprises a plurality of filters, eachof the plurality of filters is coupled to a respective one of theplurality of piezoelectric sensor elements.
 6. The system of claim 1,wherein the piezoelectric sensor is coupled to the filter via anattenuation circuit.
 7. The system of claim 1, wherein the filter iscoupled to the object type identification circuit via an analog todigital converter, and the object type identification circuit is adigital circuit.
 8. The system of claim 1, wherein the piezoelectricsensor is mounted in a vehicle bumper.
 9. The system of claim 1, whereinthe piezoelectric sensor is embedded in a dielectric layer.
 10. A methodfor identifying a type of object impact, the method comprising the actsof: receiving an object impact signal; filtering predeterminedfrequencies from the object impact signal to produce a filtered signal;identifying a type of object impact based on an analysis of the filteredsignal.
 11. The method of claim 10, further comprising the act of:attenuating the received object impact signal, wherein the attenuatedobject impact signal is filtered.
 12. The method of claim 10, wherein ifit is determined that a particular type of object has impacted, themethod further comprises the act of: activating an object impactprotection system.
 13. The method of claim 12, further comprising theacts of: receiving a speed sensor signal; and determining whether thespeed sensor signal is within a predetermined speed value range, whereinthe object impact protection system is activated only when the speedsensor signal is within the predetermined speed value range and it isdetermined that the particular type of object has impacted.
 14. Themethod of claim 10, wherein the particular type of object is apedestrian.
 15. A system, comprising: a piezoelectric sensor; means forfiltering a signal from the piezoelectric sensor to produce a filteredsignal; and means for identifying whether a particular type of objecthas impacted on the piezoelectric sensor based on an analysis of thefiltered signal.
 16. The system of claim 15, comprising: means fordeploying an object protector if the particular type of object hasimpacted on the piezoelectric sensor.
 17. The system of claim 15,wherein the particular type of object is a pedestrian.
 18. The system ofclaim 15, wherein the piezoelectric sensor comprises a plurality ofpiezoelectric sensor elements, and the means for filtering comprises aplurality of means for filtering, each of the plurality of means forfiltering is coupled to a respective one of the plurality ofpiezoelectric sensor elements.
 19. The system of claim 15, wherein thepiezoelectric sensor is coupled to the means for filtering via anattenuation circuit.
 20. The system of claim 15, wherein the means forfiltering is coupled to the means for identifying via an analog todigital converter.
 21. The system of claim 15, wherein the piezoelectricsensor is mounted in a vehicle bumper.